My guess would be that a bullet designed to expand at the lower velocities attained in short-barreled pistols might over-expand at higher velocities which, in turn, could adversely affect penetration depths. I can't think of a good reason not to use regular ammo in pistols with normal length barrels.

A good, general rule to follow is to "use the right tool for the job."

I carry the short barrel GD in my p2000sk and EMP 9mm. The standard in my other pistols. I had feeding issues with my emp with the standard so stocked up on the short barrel. Id use the standard with the P30

My guess would be that a bullet designed to expand at the lower velocities attained in short-barreled pistols might over-expand at higher velocities which, in turn, could adversely affect penetration depths. I can't think of a good reason not to use regular ammo in pistols with normal length barrels.

A good, general rule to follow is to "use the right tool for the job."

+1
The Speer GDHP short barrel rounds are outstanding for what they are specifically developed for.
The 9mm GDHP Short Barrel bullet is designed for a 3.5" barrel.
Most ammo is produced for a standard 4.0" barrel (except .45 where 5.0" is considered standard).
You may be fine, but why risk early expansion and reduced penetration by running a short barrel round in a long slide?
Guess I don't understand why you want to use this round in your gun.
You should have great performance, with a little velocity boost, using regular GDHP ammo in your extended barrel.
Plus the short barrel ammo can only be purchased in the small boxes.
Where the standard GDHP Duty ammo can be had in box of 50 for not much more money.

Iff you go to Ballistics by the Inch you can get data for various calibers. Their 9mm page is BBTI - Ballistics by the Inch :: 9mm Luger Results If you click on the "Click here for a Muzzle Energy graph" link at the top of the table, you'll see that the 124gr Gold Dots have 'way more energy from a 5" barrel than from a 3" barrel. Overall, they score just below several +P loads. Fire away.

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